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People with central vision loss almost all have exaggerated fixational eye movements when compared with people with normal vision (e.g. larger amplitudes of microsaccades and ocular drifts). Central vision loss primarily results from eye diseases or disorders that affect the macular region of the retina, such as age-related macular degeneration (AMD) and Stargardt disease. The clinical wisdom is that exaggerated fixational eye movements are detrimental to vision. This forms the basis of the increasing number of clinical trials that use fixation stability (variability of eye positions during fixation) as an outcome measure to evaluate the effectiveness of interventions on age-related macular degeneration or other retinal diseases, despite the lack of causal evidence supporting or refuting a relationship between fixational eye movements and functional vision. If excessive fixational eye movements are indeed detrimental to vision for people with central vision loss, can we reduce the amount of their fixational eye movements, thus improve their fixation stability? And if so, does that lead to improved functional vision? The goal of this study is to examine the hypothesis that retinal image motion due to abnormal fixational eye movements can be modified through fixation training, with accompanied improvements in functional vision as a result.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Microsaccade adaptation | Experimental | A fixation target will be presented at the center of the display and participants will be asked to keep the target visible at all time. The investigators will measure participants' fixational eye movements continuously and when a microsaccade (small fast eye movements that occur during fixation of a visual target) is detected, the fixation target (a small dot) will jump to a different location, depending on whether the training is to adapt the microsaccades to have smaller or larger amplitudes. With trials, participants would automatically correct for the spatial errors and thus adapting their microsaccade amplitudes. Training consists of 5-6 sessions of training (about 1 hour each). These training sessions will be scheduled weekly if possible, but it is alright if the sessions are not exactly weekly. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Fixation training | Behavioral | Training (adapting) microsaccades during fixation |
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| Measure | Description | Time Frame |
|---|---|---|
| Fixation stability | Eye positions measured while participants looked at a stationary fixation target for 10 seconds, quantified as the area that captures 68% of eye positions (unit: deg^2). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Measure | Description | Time Frame |
|---|---|---|
| Visual acuity | Smallest letter that can be read on an acuity chart (Bailey-Lovie acuity chart). Unit of measurement will be in the logarithm of the minimum angle of resolution (logMAR). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
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Inclusion Criteria:
Participants with normal vision:
Participants with macular disorders:
Exclusion Criteria:
Participants with normal vision:
Participants with macular disorders:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Herbert Wertheim School of Optometry & Vision Science, University of California Berkeley | Berkeley | California | 94720 | United States |
We will report summary results for the group. Some of the outcome measures are health related and we would like to protect the participants' privacy.
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| Contrast sensitivity | The faintest (lowest contrast) letter that can be read using the Mars Contrast Sensitivity Test. Unit of measurement will be in the logarithm of the contrast sensitivity ("log units"). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Reading performance: Maximum reading speed | Maximum reading speed (unit: words per minute) measured using the MNREAD Acuity Chart (MNREAD Acuity Chart is the name of the instrument that will be used). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Reading performance: critical print size | The smallest print size (unit: logMAR) on the MNREAD Acuity Chart that still allow participants to read at their maximum reading speed. | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Orientation judgement accuracy: low spatial-frequency | Accuracy for judging the orientation (tilted to the left or right) of a low spatial-frequency grating. Unit of measurement will be in proportion-correct. | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Orientation judgement accuracy: high spatial-frequency | Accuracy for judging the orientation (tilted to the left or right) of a high spatial-frequency grating. Unit of measurement will be in proportion-correct. | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Characteristics of fixational eye movements: microsaccade rate | Fixational eye movements during the 10 seconds when participants are asked to fixate a target for fixation stability measurement (primary measurement) will be analyzed. The rate of microsaccades (fast eye movements during fixation) will be measured (unit: number per second). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |
| Characteristics of fixational eye movements: microsaccade amplitude | Fixational eye movements during the 10 seconds when participants are asked to fixate a target for fixation stability measurement (primary measurement) will be analyzed. The amplitude of microsaccades (fast eye movements during fixation) will be measured (unit: degrees). | Data will be collected immediately before (within 1 hour) the first training session and immediately after (within 1 hour) the last training session. Data will be reported when analysis is completed for all participants (target date: by June 2025). |